Have you actually found it leaking or dripping anywhere? I'd the end of the overflow drain hose wet? Mine runs best when the overflow is empty in cold engine status.
I found mine had an issue a few years ago exactly like your describing, couldn't find an actual leak but could often smell antifreeze. Found it was the top radiator hose not tightened enough, had the radiator pressure tested etc also after I found this just to be sure and it was all OK.
Have you actually found it leaking or dripping anywhere? I'd the end of the overflow drain hose wet? Mine runs best when the overflow is empty in cold engine status.